1()=C()co2 G() COS 乘 FT FT OT G()=EzS()z(+)+o(0--) 2 卷 aT 2ET cOS( Oz、2 t f ( t ) = G ( t).cos ) 2 ( ) (  G  = ESa ( ) ( )         + + − G ( t )  t cos   − = 2 1 ( ) ) 2 ) 2 cos( ( )       E F 乘 FT FT 卷